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How to make quantum entanglement last

ENTANGLEMENT, the spooky link that makes disparate quantum objects act as one, can now be topped up for as long as necessary.

Hanna Krauter at the Niels Bohr Institute in Copenhagen, Denmark, and colleagues used a laser to align the spins of two clouds of caesium atoms, entangling them. The clouds emitted photons, which allowed the entanglement to leak away. Their trick, described in a paper to appear in Physical Review Letters, was to replenish the entanglement as it escaped, maintaining the link for as long as the experiment ran. Previously, it had only been made to last for …